1. Field of the Invention
The present invention relates to a carrier conveyor comprising a main way for continuously driving carriers, a secondary way for stocking carriers and at least an auxiliary way located in the carrier transfer region between the main way and the secondary way. More particularly, it concerns a first transfer device for transferring a carrier from a waiting position in the secondary way to the main way via a first auxiliary way having retractable lugs and a second transfer device for transferring a carrier from a stop position to the secondary way via a second auxiliary way between the main way and the secondary way.
2. Description of the Prior Art
The French Pat. No. 1,239,999 discloses a stop device which stops carriers of an overhead conveyor. The carriers are driven by means of an endless chain provided with retractable lugs. The stop device is located in the region of the waiting position and ensures the stopping of carriers with predetermined spaces which correspond to the space occupied by the loads of the carriers.
The lower portion of each retractable lug is shaped as an inclined slope so as to enable the temporary stop of carriers without stopping the operation of the endless chain. The chain provided with retractable lugs advances even is the carriers are stopped by an adequate stop organ which is disengageable from the path followed by the carriers. In fact, the retractable lugs driven by the chain have their inclined slopes which slide along stops secured to the carrier bodies and which compress the release springs of the lugs at the disengaged position.
An overhead conveyor having a chain provided with retractable lugs is also described in the French Pat. No. 2,028,057. Each lug body comprises at least an inclined slope which come progressively into contact with stops fixed to the carrier bodies by means of the progressive space decrease between the driving chain and the carrier runway.
In accordance with the French Pat. No. 1,239,999, the stopping device includes the stop organ and a plurality of pedals which are disposed successively along the path followed by the carriers and upstream of the stop organ. Each pedal is mounted for rotation around a stationary shaft and is released on the carrier path by a return spring. At this disengaged position, the pedal does not stop a carrier. The first carrier upstream of the waiting position is driven by a retractable lug of the chain, causes the pivoting of the first pedal which is located upstream of the stop organ and abuts the stop organ. At this instant, the front portion of the first pedal pivots under the control of the return spring and is applied against the back roller of the first carrier body so that the first carrier is immobilized between the stop organ and the first pedal. The back portion of the first pedal downstream of the second following carrier stops the advancing of the second carrier and has the same rule as the stop organ for the first carrier. The stopping of other following carriers is carried out in a similar manner. Thus the stopping of carriers is accomplished without suspending the chain move since the retractable lugs are disengaged or retracted by sliding on the carrier stops without driving the carriers.
When the stop organ is disengaged, the first carrier is driven from the waiting position by a lug at the engaged position which come into contact with the stop of the first carrier. The first pedal is disengaged from the carrier path by means of the return spring and enables the advancing of the second carrier. This second carrier is driven by the following engaged lug which is disengaged when the second carrier is stopped by the stop organ.
During operation, this type of transfer device for an overhead carrier conveyor causes damages and an excessive abnormal wear of retractable lugs and carriers which are subjected to excessive stress. There is also a risk that the carriers will jam in the region of the waiting position, inter alia as result of a stoppage of the chain or occasional incomplete disengagement of the retractable lugs or, in general, the breaking or deforming of the retractable lugs.
In general, the operation of this type of transfer device requires frequent repairs and maintenance and causes rapid and systematic damages in the driving chain of the carriers and considerably reduces the reliability of the conveyor.